Experimental physics regroup all the disciplines of physics that are concerned with data-acquisition, data-acquisition methods, and the detailed conceptualization (beyond simple thought experiments) and realization of laboratory experiments. It is often put in contrast with theoretical physics, which is more concerned with predicting and explaining the physical behaviour of nature than the acquisition of knowledge about it.
Although experimental and theoretical physics are concerned with different aspects of nature, they both share the same goal of understanding it and have a symbiotic relation. The former provides data about the universe, which can then be analyzed in order to be understood, while the latter provides explanations for the data and thus offers insight on how to better acquire data and on how to set up experiments. Theoretical physics can also offer insight on what data is needed in order to gain a better understanding of the universe, and on what experiments to devise in order to obtain it.